This is an application for a Program Project for interdisciplinary studies of Development, Control, and Disorders of Pulmonary Alveolar Stability. The purposes of this proposal are a) to carry out studies of the physicochemical properties of lung surfactant and of the dependence of these properties on surfactant composition; b) To characterize surfactant biochemically and relate its biochemical properties to its metabolism and structural permutations; c) To localize the subcellular sites of surfactant synthesis and determine how they develop in the fetus; d) To isolate the lung cells which synthesize surfactant and observe the enzymatic processes responsible for synthesis of its critical components; e) To demonstrate the mechanisms in the fetal lung that regulate tissue maturation and formation of surfactant; f) To elucidate hormonal factors that are important in preparing the lung for extrauterine function; g) To quantify the turnover of lung surfactant and identify the physiological factors that control turnover and abundance of surfactant; h) To assess the importance of prenatal and intrapartum factors in determining the risk of neonatal respiratory distress; i) To improve non-invasive methods for measuring cardio-pulmonary function in infants and children, especially those surviving hyaline membrane disease; j) To relate the state of pulmonary function to the forms of treatment used, during the acute phase of neonatal respiratory distress; and finally, k) To observe late complications and sequelae of hyaline membrane disease and relate them to physiological characteristics of the acute disease and to the use of standard and innovative kinds of therapy.